1. Field of the Invention
The present invention relates to electronic devices used for removing radio frequency noise generated from electronic appliances such as computers, communication equipments and the like, and more particularly to a chip type capacitor for removing radio frequency noise.
2. Description of the Prior Art
FIG. 1 illustrates a multi-layer structure of a conventional triple-terminal chip type capacitor which includes a multi-layer structure of two kinds of inner electrodes, so as to decrease an equivalent serial resistance of the inner electrodes.
FIG. 1, the reference numeral 2 denotes inner electrodes electrically connected to the triple-terminal chip type capacitor shown in FIG. 2 and external terminals 4' and 4" and used as a part of the sinal line for transmitting signals. On the other hand, the reference numeral 3 denotes inner electrodes electrically connected to ground terminals 5' and 5" and used as a passage for radio frequency noise being removed.
The triple-terminal chip type capacitor is coupled between signal lines 6' and 6" and serves to remove radio frequency flowing along the signal lines.
An electrical equivalent circuit for such a triple-terminal chip type capacitor is shown in FIG. 3.
In FIG. 3, the reference characters Lp and Rp denote an inductance and a resistance component of an inner electrode used as a part of a signal line. On the other hand, the reference characters Ls and Rs denote an inductance and a resistance component of an inner electrode used as a radio frequency noise passage.
The reference numeral C denotes an electrostatic capacity provided by a dielectric layer disposed between the inner electrode 2 used as the signal line and the grounded inner electrode 3 and the reference numeral G denotes an equivalent parallel conductance which is the inverse number to the resistance of the dielectric.
Generally, the triple-terminal chip type capacitor has a multi-layer structure comprising alternately layered inner electrodes of two kinds, one being used as a part of signal line and the other being connected to ground, and dielectric layers each being interposed between each pair of layered inner electrodes. The grounded inner electrodes remove radio frequency noise flowing along with signal frequencies through the inner electrodes used as a part of signal line. The frequency of noise being removed is determined by the electrostatic capacity and the inductance of each grounded inner electrode. For removing noise of radio frequency, accordingly, the inductance of grounded inner electrodes should be reduced. The equivalent serial resistance which is a real portion of the element impedance by the dielectric layers and the grounded inner electrodes 3 of the triple-terminal chip type capacitor should be reduced, in order to prevent a generation of heat and an increase in temperature. The material of inner electrodes of the triple-terminal chip type capacitor amounts to 50% to 80% of the manufacture cost. Accordingly, it can be understood that the manufacture cost can be reduced by making the area of inner electrodes as small as possible. However, the conventional triple-terminal chip type capacitors have problems of an increase in temperature due to a heat caused by radio frequency noise being removed and of a reduced expensive manufacture cost due to a large area of inner electrodes made of an expensive material.